Nutrition dose in the early acute phase of critical illness: Finding the sweet spot and heeding the lessons from the NUTRIREA trials

Nutrition support, carbohydrate feeding and insulin sensitivity in the critically ill patient: a complex relationship

PURPOSE OF REVIEW

This review aims to summarize recent studies that highlight the complex relationship between nutrition, carbohydrate, insulin provision and glycaemic control in the critically ill patient population.

RECENT FINDINGS

Results of observational studies concur to support early hypoglycaemia and persisting hyperglycaemia as life-threatening events. In contrast, interventional studies indicate that early macronutrient restriction appears to reduce the benefits related to insulin therapy. This restriction is however associated with improved outcomes in itself. The potential role of modified enteral solutions as an adjunctive treatment to attenuate hyperglycaemia warrants further research. The selection of a therapeutic modality may also differ according to the characteristics of the setting, such as the nurse-to-patient ratio, the type and accuracy of meters, including near-continuous glucose monitoring and the availability of computer-guided protocols.

SUMMARY

There appears to be significant interplay between nutrition, including carbohydrate provision, blood glucose control and clinical outcomes. Individualized care is probably needed to define the optimal glucose target and nutritional intervention. This can differ according to the preexistence of chronic hyperglycaemia, the timing from the onset of critical illness and the clinical condition itself.

When can we start early enteral nutrition safely in patients with shock on vasopressors?

Shock is a common critical illness characterized by microcirculatory disorders and insufficient tissue perfusion. Patients with shock and hemodynamic instability generally require vasopressors to maintain the target mean arterial pressure. Enteral nutrition (EN) is an important therapeutic intervention in critically ill patients and has unique benefits for intestinal recovery. However, the initiation of early EN in patients with shock receiving vasopressors remains controversial. Current guidelines make conservative and vague recommendations regarding early EN support in patients with shock. Increasing studies demonstrates that early EN delivery is safe and feasible in patients with shock receiving vasopressors; however, this evidence is based on observational studies. Changes in gastrointestinal blood flow vary by vasopressor and inotrope and are complex. The risk of gastrointestinal complications, especially the life-threatening complications of non-occlusive mesenteric ischemia and non-occlusive bowel necrosis, cannot be ignored in patients with shock during early EN support. It remains a therapeutic challenge in critical care nutrition therapy to determine the initiation time of EN in patients with shock receiving vasopressors and the safe threshold region for initiating EN with vasopressors. Therefore, the current review aimed to summarize the evidence on the optimal and safe timing of early EN initiation in patients with shock receiving vasopressors to improve clinical practice.

Highlights in the clinical nutrition literature: A critical appraisal of current research

Within the American Society for Parenteral and Enteral Nutrition (ASPEN), the Physician Engagement Committee (PEC) was created in 2017 by the ASPEN Board of Directors with the goal of growing the physician community both nationally and internationally. The PEC meets each month throughout the year to develop educational and research initiatives. In 2022, the PEC began an initiative to systematically review and evaluate practice-changing literature annually with the overall aim to highlight these studies at the annual ASPEN conferences and to critically discuss the potential clinical implications. The objective of the held meeting session was to present identified key papers in the fields of critical care medicine, gastroenterology and hepatology, and adult internal medicine that were published in 2022, which would complement the knowledge of the pathogenesis, diagnosis, and management of nutrition topics as well as to identify areas of future research. Overall, several large-scale randomized controlled studies were identified in each of these sections, with practice-changing major results. This manuscript summarizes the information that was presented and the discussions that followed.

Parenteral Nutrition in the Critically Ill Adult: A Narrative Review

Malnutrition in adult intensive care unit patients is associated with poor clinical outcomes. Providing adequate nutritional support to the critically ill adult should be an important goal for the intensivist. This narrative review aims to delineate the role of parenteral nutrition (PN) in meeting nutritional goals. We examined the data regarding the safety and efficacy of PN compared to enteral nutrition. In addition, we describe practical considerations for the use of PN in the ICU including patient nutritional risk stratification, nutrient composition selection for PN, route of PN administration, and biochemical monitoring.

Enteral nutrition in septic shock: a call for a paradigm shift

PURPOSE OF REVIEW

The purpose of this review is to identify contemporary evidence evaluating enteral nutrition in patients with septic shock, outline risk factors for enteral feeding intolerance (EFI), describe the conundrum of initiating enteral nutrition in patients with septic shock, appraise current EFI definitions, and identify bedside monitors for guiding enteral nutrition therapy.

RECENT FINDINGS

The NUTRIREA-2 and NUTRIREA-3 trial results have better informed the dose of enteral nutrition in critically ill patients with circulatory shock. In both trials, patients with predominant septic shock randomized to receive early standard-dose nutrition had more gastrointestinal complications. Compared to other contemporary RCTs that included patients with circulatory shock, patients in the NUTRIREA-2 and NUTRIREA-3 trials had higher bowel ischemia rates, were sicker, and received full-dose enteral nutrition while receiving high baseline dose of vasopressor. These findings suggest severity of illness, vasopressor dose, and enteral nutrition dose impact outcomes.

SUMMARY

The provision of early enteral nutrition preserves gut barrier functions; however, these benefits are counterbalanced by potential complications of introducing luminal nutrients into a hypo-perfused gut, including bowel ischemia. Findings from the NUTRIREA2 and NUTRIREA-3 trials substantiate a 'less is more' enteral nutrition dose strategy during the early acute phase of critical illness. In the absence of bedside tools to guide the initiation and advancement of enteral nutrition in patients with septic shock, the benefit of introducing enteral nutrition on preserving gut barrier function must be weighed against the risk of harm by considering dose of vasopressor, dose of enteral nutrition, and severity of illness.